1. Technical Field
The invention is related to image compression devices and in particular to an image compression device for motion video images employing a neural network.
2. Background Art
The amount of digital data required to represent a high-quality video image is so great that it must be compressed in order to be transmitted over a data channel within a reasonable amount of time. A typical image compression device performs a discrete cosine transform on successive blocks of an image and then encodes the transformed data in accordance with a minimum redundancy code such as a Huffman code. A lossless compression device currently used to obtain high-quality images from spacecraft employs an adaptive code algorithm first described in R. F. Rice, "Some Practical Universal Noiseless Coding Techniques", JPL Publication 91-3, Jet Propulsion Laboratory, Pasadena, California, Nov. 15, 1991 and R. F. Rice et al., "On the Optimality of Code Options for a Universal Noiseless Coder", JPL Publication 91-2, Jet Propulsion Laboratory, Pasadena, Calif., 1991.
In many image compression applications, lossless compression is not necessary. In such applications, all possible images can be classified into a limited number (e.g., sixty-four) of basic distinguishable groups of similar images, each group represented by a single basic image. In this case, performing lossless compression on the image data wastes resources in both processing time and transmission time.
Another problem is that the imaging system may be re-directed to a different scene, for example, so that new image data is acquired which is no longer classifiable into the original set of groups of similar images. Thus, there is a need for a compression device which is adaptive to changes in the nature of the incoming image data.